Information processing apparatus

ABSTRACT

An optical disk apparatuses includes a turntable with a bearing surface, and a spindle motor for rotating the turntable. The spindle shaft has a cylindrical first shaft having an upper end flush with the bearing surface, and a second shaft having an upper end portion and arranged in the first shaft to be slidable between an engaging position in which the upper end portion projects from the upper end of the first shaft to engage a center hole of an optical disk placed on the bearing surface and a depressed position in which the upper end portion is recessed from the upper end of the first shaft to be disengaged from the optical disk. The second shaft is moved by a spindle moving mechanism from the first position to the second position when the optical disk is to be loaded on and unloaded from the turntable.

This application is a divisional of Ser. No. 08/215,577, filed Mar. 22,1994, now U.S. Pat. No. 5,500,843.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information processing apparatus forreproducing information from a disk-shaped optical information recordingmedium having a center portion, by receiving the medium and projecting alight beam on the medium.

2. Description of the Related Art

In an information processing apparatus, e.g., an optical disk apparatus,a cartridge which contains an optical disk, for use as a recordingmedium, is horizontally inserted into the apparatus through a loadingaperture, and is held in a cartridge holder. When the cartridge is fedinto a predetermined position in the cartridge holder, the holderdescends. As the holder descends in this manner, the optical disk in thecartridge is mounted on a spindle motor, and an information recordingsurface of the disk is brought close to an optical head.

The spindle motor includes a turntable for positioning the optical diskwith respect to the axial direction thereof, a spindle mounted on thecentral portion of the turntable and defining the center of rotation ofthe disk, and a motor section for rotating the spindle and theturntable.

The spindle is fitted in a center hole of the optical disk, therebycentering the disk securely. To this end, the tip portion of the spindleis tapered so that it can be easily aligned with the center hole of theoptical disk, and projects above the upper surface of the turntable. Ingeneral, the optical disk has a hub with a predetermined thickness whichdefines the center hole. In consideration of the thickness of the hub,the tip portion of the spindle should project long enough above theupper surface of the turntable.

If the spindle for positioning the center of rotation of the opticaldisk always projects above the turntable surface in this manner,however, a relatively long distance must be secured between the loadingpath of the cartridge and the turntable surface in order to avoid acollision between the cartridge and the spindle tip when the cartridgeis inserted or ejected in the horizontal direction that is, in thedirection parallel to the turntable surface along the loading path.Accordingly, the profile of the whole apparatus cannot be thinned withease.

The same problem lies on an information processing apparatus of a typesuch that the optical disk or the recording medium is received directlywithout being contained in the cartridge.

SUMMARY OF THE INVENTION

The present invention has been contrived in consideration of thesecircumstances, and its object is to provide an information processingapparatus having a thinner profile.

In order to achieve the above object, an information processingapparatus according to the present invention comprises: means forsupporting the recording medium, the supporting means including abearing surface on which the recording medium is to be placed; meanshaving an rotating shaft portion, for rotating the recording mediumplaced on the bearing surface; means for positioning the recordingmedium on the bearing surface, the positioning means being provided atthe rotating shaft portion to be movable between a first position inwhich the positioning means projects above the bearing surface to engagethe central portion of the recording medium and a second position inwhich the positioning means is recessed from the bearing surface; andmeans for moving the positioning means to the second position as therecording medium is to be placed on the bearing surface.

Another information processing apparatus according to the inventioncomprises: means for supporting the recording medium, the supportingmeans including a bearing surface on which the recording medium is to beplaced; means having an rotating shaft portion, for rotating therecording medium placed on the bearing surface; means for positioningthe recording medium on the bearing surface, the positioning means beingprovided at the rotating shaft portion to be movable between a firstposition in which the positioning means projects above the bearingsurface to engage the central portion of the recording medium and asecond position in which the positioning means is recessed from thebearing surface; first moving means for moving the recording mediumbetween a third position in which the recording medium is placed on thebearing surface and a fourth position in which the recording medium isaway from the bearing surface; and second moving means for moving thepositioning means from the second position to the first position ininterlock with the movement of the recording medium from the fourthposition to the third position.

According to the information processing apparatuses constructed in thismanner, the positioning means is movable between the first position andthe depressed position. In placing or replacing the informationrecording medium from the bearing surface of the supporting means, thepositioning means is moved to the second in which it is recessed fromthe bearing surface of the supporting means. The positioning means ismoved to the first position to engage the central portion of therecording medium only when the recording medium is placed on the bearingsurface. In inserting or ejecting the recording medium, therefore, thepositioning means never prevents the movement of the recording medium,so that the distance between a loading path of the recording medium andthe bearing surface of the supporting means can be shortened. Thus, theprofile of the whole apparatus can be thinned.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a perspective view showing a cartridge having an optical disktherein;

FIGS. 2 to 10 show an optical disk apparatus according to an embodimentof the present invention, in which:

FIG. 2 is a sectional view of the apparatus schematically showing astate in which the cartridge is received in the apparatus,

FIG. 3 is a sectional view of the apparatus showing a state in which thecartridge is in a set position for recording or reproducing operation,

FIG. 4 is a perspective view showing part of a loading mechanism of theapparatus,

FIG. 5 is a cutaway side view showing a spindle motor,

FIG. 6 is a side view showing a spindle moving mechanism at the start ofloading operation,

FIG. 7 is a side view showing the spindle moving mechanism during theloading operation,

FIG. 8 is a side view showing the spindle moving mechanism at the end ofthe loading operation,

FIG. 9 is a cutaway side view showing the spindle motor and the opticaldisk in a state immediately before the disk is set on a turntable, and

FIG. 10 is a cutaway side view showing a state in which the optical diskis set on the turntable;

FIG. 11 is a cutaway side view showing the principal part of an opticaldisk apparatus according to another embodiment of the invention; and

FIGS. 12 and 13 show an optical disk apparatus according to stillanother embodiment of the invention, in which:

FIG. 12 is a side view showing a loading mechanism at the start ofloading operation, and

FIG. 13 is a side view showing the loading mechanism at the end of theloading operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention applied to an opticaldisk apparatus will now be described in detail with reference to theaccompanying drawings.

FIG. 1 shows a cartridge 2 which is used in the optical disk apparatus.The cartridge 2 has a flat rectangular cartridge body 6 which containsan optical disk 3 for use as an information recording medium. A window 7for access to the disk 3 is formed on each side of the cartridge body 6so that part of each corresponding side of the disk 3 is exposed throughthe window. An integral double-sided shutter 5 is slidably mounted onthe cartridge body 6, whereby the windows 7 are opened and closed. Theshutter 5 is continually urged to close the windows 7 by a spring (notshown).

The optical disk 3 includes a disk body 3B and a hub 3A fixed to thecentral portion of the body 3B. The hub 3A is formed of a magneticmaterial, and has a center hole 67.

As shown in FIGS. 2 and 3, the optical disk apparatus comprises arectangular housing 12. Formed in the front face of the housing 12 is aloading slot 11 through which the cartridge 2 is loaded into or ejectedfrom the apparatus. A loading mechanism 15 (mentioned later) is arrangedin the housing 12. The cartridge 2 inserted into the housing 12 throughthe slot 11 is moved from a standby position shown in FIG. 2 to a setposition shown in FIG. 3 by the loading mechanism.

Arranged in the housing 12, moreover, are a spindle motor 4 forsupporting and rotating the optical disk 3 in the set cartridge 2 and anoptical head 16 for recording on and reproducing information from thedisk. The motor 4 is fixed to a base 14 which is set in the housing 12,and the head 16 is provided on the base 14 in a manner such that it canbe reciprocated in the radial direction of the optical disk 3 by meansof a guide mechanism (not shown) and a drive mechanism, such as a linearmotor (not shown).

As shown in FIGS. 2 to 4, the loading mechanism 15 comprises a cartridgeholder 17 for receiving and holding the cartridge 2 inserted in thedirection of arrow A through the loading slot 11. The holder 17 ismounted with a shutter operating mechanism (not shown), and the shutter5 is opened by the mechanism as the cartridge 2 is received in theholder.

A microswitch 18 for use as detecting means is provided in the innerpart of the cartridge holder 17, that is, at the forward end thereofwith respect to the loading direction of the cartridge 2. When thecartridge 2 is inserted into a predetermined position in the cartridgeholder 17 such that it presses the microswitch 18, as shown in FIG. 2, adriving signal is delivered to a cartridge holder moving mechanism 27(mentioned later) by means of a control device (not shown). As a result,the cartridge 2, along with the holder 17, is lowered to the setposition shown in FIG. 3. The fall of the holder 17 is a necessarydistance for the hub 3A of the optical disk 3 to engage a turntable 50(mentioned later) through one of the windows 7 of the cartridge 2.

In the set position, the optical disk 3 in the cartridge 2 is mounted onthe spindle motor 4, and its lower surface is situated adjacent to theoptical head 16.

As shown in FIG. 4, the holder moving mechanism 27 for raising andlowering the cartridge holder 17 together with the cartridge 2 isprovided with a pair of parallel guide plates 30 (only one of which isshown) on either side of the cartridge holder 17. These guide plates areset up on the base 14. A cam plate 31 for use as a movable cam member islocated between each guide plate 30 and the holder 17.

Two guide rollers 32A and 32B are arranged on the outer surface of eachcam plate 31, and are fitted in two horizontal guide slots 33A and 33B,respectively, in the guide plate 30. Thus, the cam plate 31 canreciprocate only in the horizontal direction between first and secondpositions (mentioned later) along the slots 33A and 33B.

Each cam plate 31 is coupled to a side face of the cartridge holder 17which faces the plate 31 across a connection mechanism 34. Theconnection mechanism 34 includes a pair of cam slots 35A and 35B formedin the cam plate 31, a pair of guide rollers 36A and 36B mounted on theside face of the holder 17 and fitted in the slots 35A and 35B,respectively, and a pair of guide end faces 30A and 30B of each guideplate 30, which extend vertically and are in contact with thecircumferential surfaces of the rollers 36A and 36B, respectively. Eachof the cam slots 35A and 35B is composed of two horizontal portions ondifferent levels and a slant portion connecting the two.

The loading mechanism 15 serving as first moving means comprises a camplate drive mechanism 40 for moving the cam plate 31 in the horizontaldirection. The mechanism 40 includes a pair of racks 42 and a pair ofpinion gears 41 in mesh with their corresponding racks. Each rack 42 isformed on the lower edge of one end portion of each corresponding camplate 31, and extends in the horizontal direction. The pinion gears 41are fixed to a shaft 47 which extends at right angles to the cam plates31. Also, the drive mechanism 40 includes a reversible motor 45 which isfixed on the base 14. The motor 45 serves to rotate the pinion gears 41with the aid of a gear train 46 and the shaft 47.

When the pinion gears 41 are rotated in the direction of arrow C of FIG.4 by means of the motor 45, each cam plate 31, having the rack 42thereon, moves in the direction of arrow D, from a first position(illustrated) to a second position in which the guide rollers 32A and32B abut against the other ends of the guide slots 33A and 33B,respectively. In response to this, the cartridge holder 17 descends inthe direction of arrow E, from an up position to a down position, guidedby the cam slots 35A and 35B and the guide end faces 30A and 30B.Accordingly, the cartridge 2 held in the holder 17 is moved from thestandby position (fourth position) shown in FIG. 2, in which it canavoid interfering with the spindle motor 4, to the set position (thirdposition) shown in FIG. 3 in which the cartridge is mounted on the motor4 to be ready for recording or reproducing operation.

When the pinion gears 41 are rotated reversely by the motor 45, thecartridge holder 17 is moved from the down position to the up position,and the cartridge 2 in the holder 17 is moved from the set position tothe standby position.

As shown in FIG. 5, the spindle motor 4 generally includes the turntable50 serving as supporting means, a spindle 51 provided at the centralportion of the turntable, and a motor section 52 for rotating thespindle unit and the turntable. The turntable 50 has an upper surface50A on which the optical disk 3 is placed. The spindle 51 serves as arotating shaft portion which defines the center of rotation of the disk3.

The turntable 50 is fixed to a rotor 53 of the motor section 52, androtates together with the rotor 53. The upper surface 50A of theturntable 50 serves both as a bearing surface which supports the opticaldisk 3 and a positioning surface for positioning the disk 3 with respectto the axial direction of the disk.

The spindle 51 has a dual structure which includes a first spindle 54 inthe form of a hollow cylinder and an inner second spindle 55 slidablyfitted in the bore 54A of the first spindle. The first spindle 54 isrotatably held on a motor base 56 of the motor section 52 by means oftwo ball bearings 57, and the rotor 53 is fitted on the first spindlefor integral rotation. An upper end 54C of the first spindle 54 is flushwith the upper surface 50A of the turntable 50.

The inner second spindle 55 serving as positioning means is a steppedshaft whose upper end portion is a little smaller in diameter. Likewise,the bore 54A of the first spindle 54, which is fitted with the secondspindle 55, is a stepped hole whose upper end portion is a littlesmaller in diameter. A compression coil spring 60 for use as urgingmeans is interposed between a stepped portion 55A of the second spindle55 and a stepped portion 54B of the bore 54A.

The second spindle 55 is continually pressed down to a depressedposition (a second position) (indicated by full line in FIG. 5) by meansof the urging force of the compression coil spring 60 so that its upperend 55B is recessed from the upper end 54C of the first spindle 54, thatis, the tip of the spindle 51 is depressed below the upper surface 50Aof the turntable 50.

When the second spindle 55 is raised to an engaging position (a firstposition) indicated by two-dot chain line by means of a lifting pin 66of a spindle moving mechanism 65 (mentioned later), moreover, its upperend 55B projects from the upper end of the first spindle 54. Thereupon,the respective slanting guide surfaces of the upper end 55B and theupper end 54C of the first spindle 54 become continuous with each other,thus forming a spindle tip portion having a tapered guide surface.

An annular recess 50B is formed in the upper surface of the turntable 50so as to surround the spindle 51. A ring-shaped chucking magnet 70 isdisposed at the bottom of the recess 50B, and is fixed to the rotor 53.When the optical disk 3 is placed on the turntable 50 so that the tipportion of the spindle 51 is fitted in the center hole 67 of the hub 3Aof the disk, the hub is housed in the recess 50B and magneticallyattracted to the chucking magnet 70. Thereupon, the disk 3 is held in amanner such that the lower surface of the disk body 3B is intimately incontact with the upper surface 50A of the turntable 50 so as to rotateintegrally with the turntable.

The motor base 56 is fitted with a stator core 72 which has a statorcoil 71 thereon, while a rotor magnet 73 is fixed to the inner surfaceof the rotor 53, thus forming the motor section 52.

As shown in FIGS. 6, 7 and 8, the spindle moving mechanism 65 serving asmoving means or second moving means for raising and lowering the secondspindle 55 of the spindle 51 includes an operating lever 76, which issupported on the base 14 so as to be swingable around a pivot 75. A pin66 protrudes from one end portion of the lever 76, and its distal endengages a flat lower end face 55C of the second spindle 55.

A guide roller 77 is provided on the other end of the operating lever76, and is in fitted in a cam slot 78 which is formed in one of the camplates 31. The slot 78 is composed of a descent portion 78A, horizontalportion 78B, and ascent portion 78C, which are continuous with oneanother. Thus, the lever 76 is swung around the pivot 75 as the camplate 31 moves.

When each cam plate 31 and the cartridge holder 17 are in the firstposition and the up position, respectively, the guide roller 77 issituated in the upper end portion of the descent portion 78A of the camslot 78. In this state, moreover, the lifting pin 66 protruding from theone end portion of the operating lever 76 is lowered, and the secondspindle 55 is in the depressed position with its tip recessed from theupper surface 50A of the turntable 50.

When the cartridge 2 is horizontally inserted into the predeterminedposition in the cartridge holder 17 through the loading slot 11 of thehousing 12, each cam plate 31 is moved in the direction of arrow D ofFIG. 6 by the loading mechanism 15, and the cartridge 2 and the holder17 are lowered. As the cam plate 31 moves, the guide roller 77 is movedto the horizontal portion 78B of the cam slot 78 which connects with thelower end of the descent portion 78A, as shown in FIG. 7. As this isdone, the operating lever 76 rocks clockwise (in the direction of arrowF) around the pivot 75, so that the lifting pin 66 rises. Accordingly,the second spindle 55 is pushed up to the engaging position by the pin66, and its tip projects above the upper surface 50A of the turntable50.

At this time, the cartridge holder 17 moves to the down position, andthe cartridge 2 in the holder approaches the spindle motor 4. Thereupon,the hub 3A of the optical disk 3 in the cartridge 2 is magneticallyattracted to the turntable 50 by the agency of the chucking magnet 70 inthe recess 50B of the turntable 50. Moreover, the spindle 51 of thespindle motor 4 is fitted in the center hole 67 of the disk 3, wherebythe disk 3 is centered with respect to the turntable 50.

When each cam plate 31 is moved to the second position so that theloading is finished, as shown in FIG. 8, the guide roller 77 is situatedin the upper end portion of the ascent portion 78C of the cam slot 78.As the roller 77 moves, the operating lever 76 rocks counterclockwise(in the direction of arrow G) around the pivot 75. Thereupon, thelifting pin 66 is restored to the down position (a release position),and the second spindle 55 is moved to the depressed position in whichits tip is recessed from the upper surface 50A of the turntable 50.

Referring now to FIGS. 9 and 10, the relationships between the opticaldisk 3 and the spindle motor 4 will be described further in detail.

Immediately before the optical disk 3 is set on the turntable 50, asshown in FIG. 9, the inner second spindle 55 of the spindle 51 is keptin the projecting position by the spindle moving mechanism 65, so thatits upper end portion 55B projects above the upper surface 50A of theturntable 50. Also, the slanting surface of the upper end portion 54C ofthe outer first spindle 54 and the slanting surface of the upper endportion 55B of the second spindle 55 are continuous with each other, sothat the tip portion of the spindle 51 forms the tapered guide surface.If the cartridge 2 is loaded in a manner such that the center of thecenter hole 67 of the optical disk 3 is deviated to the right from thecenter of the spindle 51 by a distance S, therefore, the position of thedisk 3 in the state of FIG. 9 can be shifted to the left (in thedirection of arrow L) to be corrected as the inner peripheral edgeportion of the hole 67 comes into contact with the guide surface of thespindle 51 when the disk 3 descends.

As shown in FIG. 10, the optical disk 3 is set on the turntable 50 in amanner such that its center hole 67 or the center hole of the hub 3A, tobe exact, is fitted on the first spindle 54. Thereafter, the secondspindle 55 is lowered. In this manner, the optical disk 3 is alignedwith respect to the turntable 50. Moreover, the hub 3A of the disk 3 ishoused in the recess 50B of the turntable 50, and is attracted to theturntable by the agency of the chucking magnet 70. Thus, the opticaldisk 3 is positioned so that the lower surface of its body 3B issupported directly on the upper surface 50A of the turntable 50.

According to the optical disk apparatus constructed in this manners, thespindle 51 for centering the optical disk 3 has the dual structureincluding the outer first spindle 54, which is located lest its upperend portion 54C project above the upper surface 50A of the turntable 50,and the inner second spindle 55, whose upper end portion 55B can projectand recede from the upper surface 50A of the turntable 50. When thecartridge 2 is loaded or unloaded, that is, when it is moved in thehorizontal direction, the second spindle 55 is lowered to the depressedposition by the spindle moving mechanism 65, lest it project above theupper surface 50A of the turntable 50. Immediately before the opticaldisk 3 is set on the turntable 50, the spindle 55 is caused to projectabove the upper surface 50A of the turntable 50, thereby centering thedisk 3.

In horizontally moving the cartridge 2, with respect to the cartridgeholder 17, to insert or eject it, the optical disk 3 and the spindlemotor 4 must be prevented from interfering with each other by moving thecartridge 2 to a position at a distance T (see FIG. 10) from the uppersurface 50A of the turntable 50. According to the present embodiment,the second spindle 55 is moved to the depressed position as thecartridge 2 moves horizontally, so that there is no possibility of thetip portion of the spindle 51 preventing the movement of the cartridge.Therefore, the distance T can be made shorter than in the case of aconventional apparatus whose spindle tip is always kept projecting abovethe upper surface of the turntable. Thus, the lift of the cartridgeholder 17 can be shortened, so that the whole optical disk apparatus canenjoy a thinner profile.

In the embodiment described above, the spindle moving mechanism 65 isdesigned so that the lower end face 55C of the inner second spindle 55is flat, and that the second spindle is pushed up by means of thelifting pin 66 protruding from the operating lever 76 which is swingablearound the pivot 75. Alternatively, however, the spindle movingmechanism may be arranged in the manner shown in FIG. 11.

According to an alternative embodiment shown in FIG. 11, the lower endface of the inner second spindle 55 is formed as a downwardly convexguide surface 55D having the shape of a gently sloping cone, and theoperating lever 76 is movable in the horizontal direction, that is, inthe direction perpendicular to the spindle 51. One end of the lever 76is connected to a solenoid/plunger 80 for use as a drive source, and thelifting pin 66 protrudes from the other end of the lever. The upper endof the pin 66 abuts against the guide surface 55D of the second spindle55. As the operating lever 67 is moved in the direction of arrow H bymeans of the plunger/solenoid 80, the lifting pin 66 pushes up thespindle 55.

In the foregoing embodiment, moreover, the loading mechanism 15 is of anup-and-down holder type such that the optical disk 3 is mounted on thespindle motor 4 by raising and lowering the cartridge holder 17 forholding the cartridge 2. Alternatively, however, the mechanism 15 may beof an up-and-down spindle motor type such that the spindle motor 4 ismoved up and down with the holder 17 fixed in place, as shown in FIGS.12 and 13.

In this embodiment, the loading mechanism 15 includes a spindle motormoving mechanism 90, for use as spindle motor moving means, in place ofthe cartridge holder moving mechanism 27 according to the firstembodiment. In the description to follow, like reference numerals areused to designate the same components as the counterparts of the firstembodiment, and a repeated description of those components is omitted.

The moving mechanism 90 includes a pair of cam plates 31 (only one ofwhich is shown) each formed having a rack 42 in mesh with a pinion gear41 which is rotated forwardly and reversely by means of a cam platedrive mechanism having the same construction as the drive mechanism 40shown in FIG. 4. Each cam plate 31 is formed having two cam slots 35Aand 35B which are each composed of two horizontal portions on differentlevels and a slant portion connecting the two. A spindle motor 4 ismounted on a support frame 91 which is integral with a motor base 56.The frame 91 is fitted with a pair of guide rollers 36A and 36B, whichengage their corresponding cam slots 35A and 35B.

When the pinion gear 41 is rotated in the direction of arrow C so thateach cam plate 31 is moved in a direction parallel to the bearingsurface of the turntable 50, i.e., in the direction of arrow D insetting the optical disk 3, the support frame 91, along with the spindlemotor 4, is raised in the direction of arrow J by the agency of theguide rollers 36A and 36B and the cam slots 35A and 35B. In this case,the lift of the frame 9 is adjusted to a necessary distance for theturntable 50 to come into contact with the disk 3 through one of thewindows 7 of the cartridge 2. Thus, the motor 4 is moved from a standbyposition shown in FIG. 12 to a set position shown in FIG. 13 in whichthe motor 4 engages the optical disk to be ready for recording orreproducing operation. As the pinion gear 41 rotates reversely,moreover, the spindle motor 4 is moved from its set position to itsstandby position in which it never interferes with the cartridge 2.

In loading or unloading the cartridge 2, the spindle moving mechanism65, in association with the movement of the cam plates 31, lowers theinner second spindle 55 to a depressed position in which it does notproject above the upper surface 50A of the turntable 50. Immediatelybefore the optical disk 3 is set on the turntable 50, the spindle 55 ismoved to an engaging position in which the spindle 55 projects above theupper surface 50A of the turntable 50, whereby the disk 3 is centered.

According to the this embodiment, the spindle motor 4 is moved betweenthe set position and the standby position by means of the movingmechanism 90 which includes a pair of cam plates 31 movable in adirection substantially parallel to the bearing surface of the turntable50, rack 42, and etc. Thus, the amount of movement of the spindle motor4 can be made short and the whole optical disk apparatus can enjoy athinner profile.

Further, the second spindle 55 is moved to the depressed position as thecartridge 2 moves horizontally, so that there is no possibility of thetip portion of the spindle 51 preventing the movement of the cartridge.Therefore, the amount of movement of the spindle motor 4 can be madeshorter than in the case of an apparatus whose spindle tip is alwayskept projecting above the upper surface of the turntable. Thus, thewhole optical disk apparatus can enjoy a thinner profile.

Although the information processing apparatus which processesinformation by receiving the cartridge 2 containing the optical disk 3,for use as an information recording medium, has been described herein,the present invention is not limited to this, and may be also applied toan information processing apparatus which directly receives the opticaldisk 3 for information processing.

What is claimed is:
 1. An information processing apparatus forreproducing data from a disk-shaped optical information recording mediumhaving a center portion, the apparatus comprising:means for supportingthe recording medium, the supporting means including a bearing surfaceon which the recording medium is to be placed; means having a rotatingshaft portion, for rotating the recording medium placed on the bearingsurface, the rotating shaft portion including a cylindrical first shafthaving an upper end flush with the bearing surface; means forpositioning the recording medium on the bearing surface, the positioningmeans including a second shaft which has an upper end portion and isarranged in the first shaft to be movable between a first position inwhich the upper end portion of the second shaft projects from the upperend of the first shaft to engage the center portion of the recordingmedium and a second position in which the upper end portion of thesecond shaft is recessed in the first shaft; first moving means formoving the recording medium between a third position in which therecording medium is placed on the bearing surface and a fourth positionin which the recording medium is away from the bearing surface; andsecond moving means for moving the positioning means from the secondposition to the first position in interlock with the movement of therecording medium from the fourth position to the third position.
 2. Aninformation processing apparatus according to claim 1, wherein thesecond moving means includes urging means for urging the second shafttoward the second position, and push means for pushing the second shaftto the first position when the recording medium is moved to the thirdposition by the first moving means.
 3. An information processingapparatus according to claim 2, wherein said first moving means includesholding means for holding the recording medium, a cam member movable ina direction substantially parallel to the bearing surface, drive meansfor moving the cam member, and connecting means for connecting theholding means to the cam member so that the holding means moves betweenthe third position and the fourth position in association with themovement of the cam member.
 4. An information processing apparatusaccording to claim 3, wherein the second moving means includes anoperating member engaging the cam member, for moving the push meansbetween a push position in which the push means pushes the second shaftand a release position in which the push means releases the second shaftfrom the push position, in association with the movement of the cammember.
 5. An information processing apparatus according to claim 2,wherein the second shaft includes a lower end which is opposite to theupper end portion and has a convex guide surface, and the second movingmeans includes drive means for moving the push means along the guidesurface.
 6. An information processing apparatus according to claim 1,wherein said recording medium includes a hub provided on the centerportion thereof, said hub being formed of a magnetic material, andwherein the bearing surface includes a recess formed therein forreceiving the hub of the recording medium when the recording medium isplaced on the bearing surface, said recess having a magnet arrangedtherein for magnetically attracting the hub so that the recording mediumis urged into tight contact with the bearing surface.